New Properties of Secondary Cosmic-Ray Lithium, Beryllium and Boron - PowerPoint PPT Presentation

New Properties of Secondary Cosmic-Ray Lithium, Beryllium and Boron Measured by AMS M. Paniccia (DPNC - University of Geneva, Switzerland) on behalf of the AMS Collaboration

Secondary Cosmic Rays 1 Lithium, Beryllium and Boron, as well as elements in the sub-Fe group, are much more abundant in cosmic rays than in the solar system: they are not direct products of cosmic-ray sources Horandel Adv. Space. Res . 41 (2008) 442-463 C N O Fe Sc-Ti-V-Cr-Mn Li-Be-B

2 Secondary Cosmic Rays Lithium, Beryllium and Boron are mostly produced from collision of primary cosmic rays, such as Carbon and Oxygen, with the interstellar medium (ISM). Primary (p, He, C, O, …) Galactic Halo ISS Secondary (Li, Be, B, …) Galactic Disk Cosmic rays are commonly modeled as a relativistic gas diffusing into a magnetized plasma. Diffusion models based on different assumptions predict a Secondary/Primary ratio asymptotically proportional to R δ . With Kolmogorov turbulence model a δ = -1/3 is expected, while Kraichnan theory leads to δ = -1/2 .

3 Secondary Cosmic Rays and origin of spectral breaks C. Evoli (2019) If the hardening in CRs is related to the injected If the hardening is related to propagation spectra at their source, then similar hardening properties in the Galaxy then a stronger is expected both for secondaries and primary hardening is expected for the secondary with cosmic rays. respect to the primary cosmic rays. See also Serpico J. Astrophys. Astr. (2018) 39-41

AMS CRs Chemical Composition 4 AMS has collected > 144 billion cosmic rays up to today. With such a statistics secondary cosmic rays can be measured with high precision H He Analyzed C Li B N O Be Ne Mg Si Na F Al Analysis in progress S P Cl Ar K Ca Cr Fe Sc Ti V Mn Ni Co

Lithium and Boron Fluxes 5 Identical above ~ 7 GV. M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101 Lithium 1.9 M Boron 2.6 M

6 Beryllium and Boron Fluxes Identical above ~ 30 GV. Effect of unstable 10 Be component. M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101 Beryllium 0.9 M Boron 2.6 M

7 Li, Be and B Fluxes in Kinetic Energy Over the last 50 years, only a few M. Aguilar et al. Phys. Rev. Lett. 120 (2018) 021101 experiments have measured the Li and and Be fluxes above a few GV. Typically, these measurements have errors larger than 50% at 50 GeV/n. For the B flux, measurements have errors larger than 15% at 50 GeV/n. AMS-02 has dramatically improved this situation: the total error on each of the fluxes is 3%–4% at 50 GeV/n.

8 Primary and Secondary Fluxes 3 M. Aguilar et al. Phys. Rev. Lett. 120 (2018) 021101 10 × 4 ] Helium Helium 1.7 Carbon ( × 30) Carbon x 30 (GV) Oxygen ( × 28) Oxygen x 28 3 -1 sr -1 s -2 2 [ m 2.7 R ~ 1 × Lithium ( × 200) Lithium x 400 Flux Beryllium ( × 400) Beryllium x 200 Boron ( × 145) Boron x 145 0 3 3 2 2 30 10 2 10 10 2 10 × × ~ Rigidity R [GV]

9 Primary and Secondary Spectral Indices Deviate from single power law above 200 GV. Secondaries hardening is stronger. Lithium Helium Beryllium Carbon Boron Oxygen M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101

10 Secondary/Primary Flux Ratios M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101 Li/C Li/O AMS published high precision data of: Li/C , Be/C , B/C , Li/O , Be/O , and B/O . Δγ = 0.13 ± 0.06 Δγ = 0.19 ± 0.06 Data were fit with power laws in the rigidity intervals Be/C Be/O [60.3 GV – 192 GV] and [192 GV – 3300 GV]. Δγ = 0.09 ± 0.07 Δγ = 0.15 ± 0.07 All ratios show a hardening (~ 2σ), i.e. secondaries exhibit a B/C B/O stronger hardening than primaries. Δγ = 0.09 ± 0.05 Δγ = 0.14 ± 0.05

11 Secondary/Primary Spectral Indices M. Aguilar et al., Phys. Rev. Lett. 120 (2018) 021101 192 GV 192 GV Li/C Li/O -0.2 -0.2 Be/O Be/C B/O B/C Δ Spectral Index -0.3 -0.3 -0.4 -0.4 ~ ~ Rigidity R [ G V ] Rigidity R [ G V ] -0.5 -0.5 3 3 2 2 3 3 2 2 60 10 2 × 10 10 2 × 10 60 10 2 × 10 10 2 × 10 Combining the six secondary/primary ratios a global hardening at 192 GV of 0.13 ± 0.03 is observed. This observation favors the hypothesis that the flux hardening is an universal propagation effect . A. E. Vladimirov et al., Astroph. J. 752 (2012) 68 P. Blasi et al., Phys. Rev. Lett. 109 (2012) 061101 N. Tomassetti, Phys. Rev. D 92 (2015) 081301(R) … 11

Nitrogen Flux 12 Cosmic-ray Nitrogen nuclei are partly primaries and partly secondaries. AMS-02 model-independent estimation of abundance at the source: M. Aguilar et al., Phys. Rev. Lett. 121 (2018) 051103 Nitrogen 2.2 M Φ N = (0.090±0.002) × Φ O + (0.62±0.02) × Φ B

Prospects: 13 Boron to Carbon ratio Preliminary AMS 7 years data. Please refer to the AMS forthcoming publication in PRL.

15 Prospects H He Fe C He H BeB C Li N O sub-Fe/Fe Ne Mg Si Na F Al S P Cl Ar K Ca Fe Cr Sc Ti V Mn Ni Co

16 Conclusions Using the first five years of AMS-02 data, Lithium, Beryllium and Boron fluxes have been measured from 1.9 GV to 3.3 TV, with 1.9M, 0.9M and 2.6M nuclei respectively with a typical accuracy of 3-4% at 100 GV. The three fluxes deviate from a single power law above 200 GV in an identical way. This hardening is larger than the one observed for primary species (He, C, O). The secondary/primary flux ratios Li/C, Be/C, B/C, Li/O, Be/O, and B/O were measured taking into account correlations on systematic errors. The secondary/primary flux ratios show an average hardening of 0.13 ± 0.03. These observations favor the hypothesis that the flux hardening is an universal propagation effect. The Nitrogen spectrum has been measured from 2.2 GV to 3.3 TV, with 2.2M events. The flux is described by the sum of a primary (Oxygen) and a secondary (Boron) component. The model independent N/O ratio at source of 0.09 ± 0.02 is derived. The accuracy of the secondary cosmic ray nuclei fluxes will be significantly improved, in particular at the highest rigidities, during the lifetime of the ISS (to at least 2028) Heavier nuclei secondary fluxes will be measured, probing origin and propagation of cosmic rays at high mass and charge.